This invention generally relates to paper products as well as a method and glue formulation for making same. More particularly, this invention includes paper products that have portions thereof which are adhered to each other by a rapidly setting aqueous animal glue formulation that includes a salt component for enhancing the tack while maintaining a low viscosity, which formulation has an adequate pot life while setting within seconds when applied to the paper substrate. In an important aspect of this invention, the paper article is a roll of newsprint wrapped within a kraft paper cover that is glued together by an automated procedure.
When large rolls of newsprint paper are manufactured at pulp- and paper-making facilities, the rolls of newsprint thus produced are typically wrapped in protective kraft paper overcover shortly after the large newsprint rolls are made in order to thereby protect the rolls from becoming damaged and soiled during transport and storage. Each such paper overcovering is adhered to itself along appropriate seams such that the paper overcover generally conforms to the shape and size of the newsprint roll being wrapped. In this industry, it is important to accomplish this step of adhering the overcover together in a manner that is susceptible to automated and rapid handling.
In the past, these objectives were accomplished by utilizing pumpable hot melt adhesives to bond the overcover paper together along its seams. Hot melt adhesives are particularly suitable in this regard because they can be readily applied by devices that heat, pump and apply the adhesive to a directed location, such as by extruding. These types of adhesives are very suitable for use in these devices because they are flowable at temperatures above their melting points, typically on the order of 300.degree. to 350.degree. F. Such hot melt adhesives are applied in this flowable state and, after application, rapidly cool to a substantially solidified state at which they bond the roll wrapping cover over the roll of newsprint. Equipment for this procedure has been widely accepted in the paper-making industry, and hot melt adhesive application equipment of this type has been in wide use for a number of years.
One difficulty that has become increasingly more important over the years has been the fact that hot melt adhesives are primarily resins and polymers that are water-insoluble. Such hot melt adhesives must be used at somewhat high temperatures, they are difficult to clean from within applicator machinery, and they are more expensive than glues. Additionally, it is not possible to repulp the large paper overcovers after they have served their purpose of protecting the newsprint rolls. In the past, any attempted repulping of these overcovers would require special handling by removing that portion of the overcover having the hot melt adhesive adhered thereto or by carrying out some other special treatment procedure. Quite often, these roll wrapping overcovers would be discarded or incinerated, rather than being included within the repulping stock. This results in waste of a valuable natural resource.
Accordingly, there is a need for a new approach whereby the advantages of automated and rapid handling can be maintained while eliminating the undesirable effects that are attendant to the use of hot melt adhesives. It would be particularly desirable if this new approach would also maintain the use of the adhesive pumping and extruding equipment that is in wide use in this industry today.
The present invention achieves all of these objectives and advantages by devising an approach whereby a glue formulation having substantial quantities of animal protein glue is heated, pumped and applied, preferably by conventional hot melt adhesive applicators, to a paper article such as a newsprint roll overcover in order to adhere the paper article along a seam thereof. The glue formulation is a water-soluble blend of animal protein derived from a collagen, water, and a water-soluble salt which is divalent at the pH of the total system of the glue formulation. The salt, in combination with other components of the glue formulation, provides a glue formulation that is of enhanced tack and that is rapidly setting, while being pumpable at elevated temperatures lower than those typical of the application temperature of a hot melt adhesive.
It is accordingly an object of the present invention to provide an improved paper article, method of manufacture thereof, and glue formulation utilized therein.
Another object of the present invention is to utilize a glue formulation that is applied at elevated temperatures to cellulosic material, which glue formulation includes divalent anions to enhance its tack and shorten its setting time.
Another object of the present invention is to provide an improved paper article having portions adhered together by an animal based glue formulation that is extruded at an elevated temperature.
Another object of this invention is to provide an improved approach for wrapping newsprint rolls at the paper-making mill which utilizes currently used adhesive application equipment.
Another object of the present invention is to provide a roll-wrapping glue formulation which renders the wrapped roll completely repulpable.
Another object of this invention is to utilize a glue formulation applicator at temperatures lower than application temperatures of hot melt adhesives and in conjunction with a glue formulation that is more easily cleaned up and less costly than hot melt adhesives.